phone: Explicitly disable pipewire

Somehow pipewire got enabled by something else in the config. By
explicitly disabling it, we're able to make phone calls work again.

hosts/phone/configuration.nix

@@ -1,4 +1,4 @@
-{ self, pkgs, ... }:
+{ self, pkgs, lib, ... }:
 
 let
   inherit (builtins) attrValues;
@@ -53,6 +53,8 @@ in
     calls.enable = true;
   };
 
+  services.pipewire.enable = lib.mkForce false;
+
   networking = {
     wireless.enable = false;
     wireguard.enable = true;